Since 1998, at least one-third of the members of the
National Assembly must be people with a learning disability. From 1980 the actor
Brian Rix represented the charity in a number of positions, including
Secretary-General,
Chairman and finally
President. Until October 2019, the chief executive of Mencap was Jan Tregelles, succeeding
Mark Goldring in March 2013. Tregelles first worked at Mencap in 1983 as PA to one of the then directors. She has held various posts across Mencap; she has been the director of personal support since 2002 and has grown the business from £80 million turnover to £180 million in that time. In the summer of 2019, Tregelles announced that she would be leaving Mencap. She was succeeded by Edel Harris in October 2019. In March 2022, the charity announced the appointment of
Dame Carolyn Fairbairn as its new Chair, replacing Derek Lewis after his eight-year term. In July 2023, Edel Harris announced she was stepping down as CEO. Jackie O'Sullivan, previously Mencap's Executive Director of Communication, Advocacy & Activism was installed as interim CEO. In January 2024, Mencap announced Jon Sparkes OBE, formally CEO of
UNICEF UK would be installed as CEO in June 2024. == Supporters and ambassadors ==